Transparency in reporting of conflict of interest is an increasingly important aspect of publication in medical journals. Publication of large industry-supported trials may generate many citations and journal income through reprint sales and thereby be a source of conflicts of interest for journals. We investigated industry-supported trials' influence on journal impact factors and revenue.

Methods and Findings

We sampled six major medical journals (Annals of Internal Medicine, Archives of Internal Medicine, BMJ, JAMA, The Lancet, and New England Journal of Medicine [NEJM]). For each journal, we identified randomised trials published in 1996–1997 and 2005–2006 using PubMed, and categorized the type of financial support. Using Web of Science, we investigated citations of industry-supported trials and the influence on journal impact factors over a ten-year period. We contacted journal editors and retrieved tax information on income from industry sources. The proportion of trials with sole industry support varied between journals, from 7% in BMJ to 32% in NEJM in 2005–2006. Industry-supported trials were more frequently cited than trials with other types of support, and omitting them from the impact factor calculation decreased journal impact factors. The decrease varied considerably between journals, with 1% for BMJ to 15% for NEJM in 2007. For the two journals disclosing data, income from the sales of reprints contributed to 3% and 41% of the total income for BMJ and The Lancet in 2005–2006.

Conclusions

Publication of industry-supported trials was associated with an increase in journal impact factors. Sales of reprints may provide a substantial income. We suggest that journals disclose financial information in the same way that they require them from their authors, so that readers can assess the potential effect of different types of papers on journals' revenue and impact.

Editors would like to imagine they are simply gatekeepers who facilitate the interaction between authors who wish to impart information and people who want to read it. In fact, they are subject to a raft of external pressures that interfere with this core task. Coauthors are prone to disputes with each other and with reviewers; rejected authors may protest; readers may be dissatisfied; institutions may react inadequately to editors' concerns about probity; editorial freedom may be compromised by the demands of the learned society that owns the journal; and a commercial publisher might exert subtle—or unsubtle—pressure to increase profitability. All of these distractions increase the possibility of competing interests corrupting the editorial process.

Influence of the Impact Factor Top

Added to this toxic mixture is the impact factor (IF). Just as many clinicians claim that contacts by pharmaceutical company representatives do not affect their prescribing behaviour, so editors are likely to deny that thoughts of a rising IF might influence their acceptance rates. In their paper published this week in PLoS Medicine, Andreas Lundh and colleagues analysed randomised controlled trials published in six high-impact general medical journals during two time periods a decade apart; they calculated the putative fall in IF that would have occurred had publication been denied to papers that were commercially sponsored.